This invention relates generally to fuel-oxygen burners and more specifically to pulsed fuel-oxygen burners for rotatable workpieces.
High-purity quartz tubes are currently produced for use in the silicon chip processing industries. One method of manufacturing large outside diameter quartz tubes, for example, between about 300 mm to about 500 mm outside diameter quartz tubes, is to resize smaller diameter quartz tubes, for example, quartz tubes having an outside diameter of less than about 250 mm.
One method of performing this resizing operation is analogous to glass-blowing. A quartz tube is mounted horizontally on a rotating lathe. The interior of the quartz tube is slightly pressurized, while the outside of the quartz tube is heated by natural gas-oxygen jet flames, which jet flames impinge upon the outside of the rotating quartz tube. The burners are first positioned at one end of the quartz tube and are slowly translated down the length of the quartz tube. The heat from the impinging flames soften the quartz, thus allowing the tube to expand due to the internal pressure. This quartz tube is rotated to maintain a circular cross-section and to distribute the heat from the flames evenly around the circumference of the quartz tube.
A conventional process typically increases the diameter of a quartz tube by about 50 mm with a single pass of the burners, which pass may require up to about 45 minutes, depending on the length of the tube. Larger diameter increases are achieved by making multiple passes of the burners down the length of a tube.
One drawback of this method of resizing is the large amount of natural gas and oxygen consumed by the burners. The cost of resizing a quartz tube can be as high as $30/lb. of quartz, mostly comprising the cost of the natural gas and oxygen. This high cost is due, in part, to low efficiency of transferring heat from the burning natural gas-oxygen jet to the rotating quartz tube. Improving heat transfer from the burning natural gas oxygen jets to the rotating quartz tube could result in substantial fuel and oxygen cost savings. Additionally, increasing the rate of heat transfer from the flame to the tube could reduce processing time and increase productivity.
Accordingly, there is a need in the art for an improved fuel-oxygen burner and application for quartz tube resizing.